Dual spring flow control valve

Abstract

An electropneumatic proportional flow control device improves electropneumatic control of pneumatically operated valves. Improved turn down ratios in regards to the electromagnetic response of the device to a supplied control voltage is achieved using two variable spring devices, one linear, as part of the pressure regulator valve component, and the other non-linear, as part of the proportional valve component and which are magnetically responsive to different magnetic forces. The use of both the linear and non-linear springs together results in an increased turndown-ratio, especially during initial valve control.

Description

FIELD OF THE INVENTION[0001]The present invention relates generally to a device for electromagnetic control of pneumatically operated valves and, more specifically to such a valve having an armature design and method of operation such as to allow improved turndown ratios.BACKGROUND OF THE INVENTION[0002]Numerous types of proportional pneumatic flow control valves are presently available which accurately control flow over a wide range of flow control applications. However, a problem with current flow control valves is that they generally do not offer precision flow at lower rates. For balanced valves the valve percentage of error for the full scale of the valve may be too great; and, the low flow imprecision can be too problematic to the application. As such, to control such a system with PID controllers to eliminate such wide swings that are inherent within the system remains very difficult.[0003]Unbalanced valves are (usually) simpler designed, smaller valves with low pressure drop...

AI Technical Summary

Benefits of technology

The present invention provides an improved valve design and operation using a special electropneumatic device that allows for improved turndown ratios. The valve uses two variable spring devices, one linear and one non-linear, which work together to achieve precision control over the initial liftoff current and improved control over higher flow rates. The use of both springs results in an increased turndown-ratio, especially during initial valve control. The valve is small, lightweight, and insensitive to position or vibration, making it ideal for use in medical products.

Problems solved by technology

However, a problem with current flow control valves is that they generally do not offer precision flow at lower rates.

For balanced valves the valve percentage of error for the full scale of the valve may be too great; and, the low flow imprecision can be too problematic to the application.

As such, to control such a system with PID controllers to eliminate such wide swings that are inherent within the system remains very difficult.

Disadvantages include a limited sizes, since with a large unbalanced valve the forces needed to seat and hold the flow often becomes impractical.

However, such a solution creates an additional leak path and at a cost that is generally higher.

In trim control applications, the selection of balanced or unbalanced designs is not entirely straightforward, and will ultimate be based upon the selection and design of the actuator.

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